Conventionally, there has been available a vehicle headlamp apparatus for driving at night (e.g., see patent document 1). The apparatus can change a swivel angle in the optical axis direction (light distribution direction) of a headlamp at the vehicle front in response to a steering angle within an area approximately parallel to a road surface.
Generally, a driver drives a vehicle by visually checking a road forward in the traveling direction. When there is a curve in the vehicle's traveling direction, the driver feels wanting to visually check ahead of the curve before the vehicle enters the curve.
There may be a need for controlling a swivel angle according to the steering angle as mentioned above. The headlamp's light distribution direction does not follow the curve direction until the driver operates a steering system. Accordingly, the above-mentioned conventional vehicle headlamp apparatus may not sufficiently ensure the driver's visibility caused by the headlamp's light distribution.
To respond to changes in the curvature of a road shape ahead, there is proposed a vehicle headlamp apparatus based on navigation-cooperative control (e.g., see patent document 2). The apparatus is combined with a navigation system that associates position information obtained from a position detection unit such as the GPS (Global Positioning System) with map information. The apparatus is constructed to control the headlamp's swivel angles in cooperation with the navigation system. The vehicle headlamp apparatus based on navigation-cooperative control selectively enables a steering angle control mode and a navigation-cooperative control mode. The steering angle control mode controls optical axis directions for the headlamp in accordance with steering angles. This aims at concurrently providing stable control of headlamp's swivel angles during cornering and appropriate control of headlamp's swivel angles during curvature changes at entry into or exit from a corner.
There may be a case of changing between the steering angle control mode and the navigation-cooperative control mode in the above-mentioned vehicle headlamp apparatus based on navigation-cooperative control. In this case, the headlamp's swivel angle (light distribution direction) suddenly makes discontinuous changes, causing the driver to feel uncomfortably.                Patent document 1: JP-S61-211146A        Patent document 2: JP-3111153 B2 (U.S. Pat. No. 5,588,733)        